Alex Brown, a senior at Guilford High School in Connecticut, is taking two AP classes: statistics and chemistry.

“They’re both really intense,” she says. “I don’t think people understand how much AP classes actually take out of us. It’s going to be really rough.” Then she laughs nervously.

More high school students than ever are taking Advanced Placement courses, the College Board announced. And, they are doing better on the exams. The average score rose to 2.83 from 2.80, out of a maximum of 5.

Yet despite all the hard work, students like Brown may not be able to place out of required college courses or even skip freshman year if they score well on the AP tests. Some prestigious colleges have stopped giving academic credit for AP tests scores.

Brown doesn’t. Several departments at Columbia don't*, and most recently, Dartmouth said it won’t let AP students skip ahead to an early graduation.

“We want a Dartmouth education to take place at Dartmouth,” says school spokesman Justin Anderson.

Translation: APs aren’t Dartmouth. Will more schools follow suit? David Conley, a professor at the University of Oregon and CEO of the Educational Policy Improvement Center, says: No.

“We’ve always seen a certain group of colleges not give much credit to AP. It’s not unusual and not new,” he says. “They’re highly selective and can get away with that.”

Conley says prestigious schools can afford to be picky about what credits to accept. But there are “more general admissions schools where they want students to bring AP credits and they do want to reward them for doing that.” In other words, AP credit is like bait for the best students.

Behind this question of college credit for AP tests is a deep-seated anxiety felt by educators that students aren’t prepared for college.

“Three out of four students who get to college come lacking in foundation and strong skills that a good college education requires,” says Carol Geary Schneider, president of the Association of American Colleges and Universities.

Specifically, she says students lack skills in research, writing, and evidence-based analysis. Schneider says the general problem of college readiness “raises questions about whether the courses students took in high school, that might’ve been labeled AP or dual enrollment, were really providing students the preparation in writing and research that college itself will emphasize. Different institutions are making different judgments about that.”

Ken Bernstein, a retired teacher who writes on education, thinks more schools might join Dartmouth, Brown and Columbia on the AP question. Even though a third of high school students are taking AP tests, he says, “There aren’t that many kids prepared at a college level. Let’s be realistic.”

Trevor Packer, a Vice President at the College Board, the organization that runs the AP tests, points out that AP scores weren’t originally used as a replacement for college credit.

“The original use in 1956…was as a tool for placing students appropriately”, he says. That means determining whether a student should be in French II instead of French I, but not about placing out of French altogether.

Packer says the College Board is revamping the AP exams to make them more rigorous. But there is no question, he adds, that APs are making students more prepared for college.

“The research does consistently show that students who participate in AP courses in high school and earned a score of 3 or better perform at a higher level than matched peers,” he says.

Even if some top schools aren’t giving college credit, AP tests look good on high school transcripts. So they may not let students get out of freshman year, but they’ll help them get into college in the first place.

*CORRECTION: An earlier version of this story said Columbia doesn’t award college credit for AP exams. The statement was based on information from a Columbia admissions officer, who misspoke. Under certain circumstances, some departments at Columbia give credit for AP exams, thus reducing the number of courses those students are required to take in order to graduate. The text has been revised.